A man, who had previously murdered his adoptive parents, has been executed by lethal injection in the US after being convicted of killing a police officer in Texas 11 years ago.

Daniel Joe Hittle, 50, was the 39th execution this year in Texas. He had been accused of killing five people on November 15, 1989, including a four-year-old girl.

However, he was tried only for the murder of policeman Gerald Walker, 48, who had pulled Hittle over for speeding.

Hittle had been freed from a Minnesota prison in 1984 after serving 11 years of a 30-year term for killing his adoptive parents who were stabbed after Hittle became enraged because he believed their dog had scratched his truck.